U.S. patent application number 10/669203 was filed with the patent office on 2005-03-24 for energy activated vaso-occlusive devices.
This patent application is currently assigned to Scimed Life Systems, Inc.. Invention is credited to Wallace, Michael P..
Application Number | 20050065501 10/669203 |
Document ID | / |
Family ID | 34313677 |
Filed Date | 2005-03-24 |
United States Patent
Application |
20050065501 |
Kind Code |
A1 |
Wallace, Michael P. |
March 24, 2005 |
Energy activated vaso-occlusive devices
Abstract
A vaso-occlusive device for treating a site within a patient's
vasculature, the device comprising a material which may be heated
by application of a source of energy external to the body after the
device is implanted at a treatment site in a patient's body. The
device is introduced in a cavity of a patient's vasculature, such
as an aneurysm, after which an external energy source, such as a
MRI machine is activated to heat the vaso-occlusive device to
assist in forming a thrombus or embolism within the treatment site,
to release and/or activate a diagnostic or therapeutic agent
carried by the vaso-occlusive device, and/or to fuse together
portions of the vaso-occlusive device to help stabilize the device
in a three-dimensional shape.
Inventors: |
Wallace, Michael P.;
(Fremont, CA) |
Correspondence
Address: |
Bingham McCuthen, LLP
Three Embarcadero, Suite 1800
San Francisco
CA
94111-4067
US
|
Assignee: |
Scimed Life Systems, Inc.
Maple Grove
MN
|
Family ID: |
34313677 |
Appl. No.: |
10/669203 |
Filed: |
September 23, 2003 |
Current U.S.
Class: |
606/1 ;
606/108 |
Current CPC
Class: |
A61B 2017/005 20130101;
A61B 17/12154 20130101; A61B 17/12022 20130101; A61B 17/12145
20130101; A61B 17/12113 20130101 |
Class at
Publication: |
606/001 ;
606/108 |
International
Class: |
A61B 017/00; A61F
007/00; A61F 007/12; A61F 011/00 |
Claims
What is claimed:
1. A vaso-occlusive device for treating a site within a patient's
vasculature, the device comprising a first material which may be
heated by application of a source of energy external to a patient's
body after the device is implanted at a treatment site in the
patient's body.
2. The vaso-occlusive device of claim 1, further comprising a
second material having a melting or glass transition temperature
greater than body temperature, but less than a temperature reached
by the device when heated directly or indirectly by the external
energy source.
3. The vaso-occlusive device of claim 2, wherein the second
material is embedded in one or more portions of the device, such
that, when heated directly or indirectly by the external energy
source and allowed to cool in the body, the one or more portions
are at least partially fused together to stabilize the
vaso-occlusive device in a deployed configuration.
4. The vaso-occlusive device of claim 2, the second material
comprising a coating provided on at least a portion of the
device.
5. The vaso-occlusive device of claim 4, further comprising a
bioactive agent that is released at the treatment site when the
coating is heated.
6. The vaso-occlusive device of claim 1, further comprising a
bioactive agent that is activated when the device is heated.
7. The vaso-occlusive device of claim 1, the first material
comprising a ferrous material, and the external energy source
comprising magnetic resonance.
8. The vaso-occlusive device of claim 1, wherein the first material
is embedded in the device.
9. The vaso-occlusive device of claim 1, wherein the first material
is in a coating provided on at least a portion of the device.
10. The vaso-occlusive device of claim 1, the device comprising a
coil forming a lumen, and a heating member disposed in the lumen,
the heating member at least partially comprising the first
material.
11. The vaso-occlusive device of claim 10, the heating member
comprising a filament attached to first and second locations of the
coil.
12. The vaso-occlusive device of claim 10, further comprising a
second material having a melting or glass transition temperature
greater than body temperature, but less than a temperature reached
by the heating member when heated directly or indirectly by the
external energy source.
13. The vaso-occlusive device of claim 12, wherein the second
material is embedded in one or more portions of the coil, such
that, when heated by the heating member and allowed to cool in the
body, the one or more portions are at least partially fused
together to stabilize the coil in a deployed configuration.
14. The vaso-occlusive device of claim 12, the second material
comprising a coating provided on at least a portion of the
coil.
15. The vaso-occlusive device of claim 14, further comprising a
bioactive agent that is released at the treatment site when the
coating is heated.
16. The vaso-occlusive device of claim 12, the heating member
comprising a filament attached to the coil, the second material
comprising a coating provided on at least a portion of the
filament.
17. The vaso-occlusive device of claim 16, further comprising a
bioactive agent that is released at the treatment site when the
coating is heated.
18. A vaso-occlusive device comprising a helically wound coil
comprising a highly conductive material and forming a lumen, and a
filament at least partially positioned in the lumen, the filament
comprising a highly resistive material, such that, when the device
is implanted in a body and exposed to a pulsed magnetic field
applied from outside the body, the highly resistive material is
heated.
19. The vaso-occlusive device of claim 18, the highly conductive
material comprising platinum, the highly resistive material
comprises ferrous material.
20. A vaso-occlusive device for treating a site within a patient's
vasculature, comprising: a first, ferrous material that, when the
device is implanted at a treatment site in the patient's body, can
be heated by application of a pulsed magnetic field applied by a
magnetic resonance ("MR") device located external to the patient;
and a second material having a melting or glass transition
temperature greater than body temperature, but less than a
temperature reached by the ferrous material when heated by the MR
device.
21. The vaso-occlusive device of claim 20, wherein the second,
material is embedded in one or more portions of the device, such
that, when the device is heated due to the ferrous material being
heated by the MR device, and allowed to cool in the body, the one
or more portions are at least partially fused together to stabilize
the vaso-occlusive device in a deployed configuration.
22. The vaso-occlusive device of claim 20, the second material
comprising a coating provided on at least a portion of the
device.
23. The vaso-occlusive device of claim 22, further comprising a
bioactive agent that is released at the treatment site when the
coating is heated.
24. The vaso-occlusive device of claim 20, further comprising a
bioactive agent that is activated when the device is heated.
25. The vaso-occlusive device of claim 20, wherein the ferrous
material is embedded in the device.
26. The vaso-occlusive device of claim 20, wherein the ferrous
material is in a coating provided on at least a portion of the
device.
Description
FIELD OF INVENTION
[0001] The invention relates generally to vaso-occlusive devices,
and, more particularly, to applying energy from a source external
to a patient's body to activate a vaso-occlusive device implanted
in a body cavity of the patient.
BACKGROUND
[0002] Vaso-occlusive devices are implants that are placed in
cavities, e.g., an aneurysm, blood vessel lumen, fistula, or other
cavity in a patient's vasculature for the purpose of facilitating
formation of an thrombus or embolism. Such vaso-occlusive devices
are typically delivered by a catheter that is advanced to a
treatment site endoluminally, e.g., from a percutaneous entry site,
using conventional access procedures.
[0003] Well known vaso-occlusive devices include helically-wound
coils that assume an elongate, "delivery" configuration when
constrained within a delivery catheter, and a three-dimensional,
"deployed" configuration when deployed in the body cavity and no
longer constrained in the catheter. Once deployed, such
vaso-occlusive devices help promote embolization and/or occlusion
of the cavity. For example, vaso-occlusive devices are used to fill
aneurysm cavities to reduce the risk of the further growth and/or
rupture of the aneurysm.
[0004] To enhance embolization, it has been suggested to provide a
coating on vaso-occlusive devices that reacts in some beneficial
way (e.g., with blood) in the body. For example, U.S. Pat. No.
6,187,024 discloses vaso-occlusive devices coated with a bioactive
agent and/or collagenous material. It has also been suggested to
provide a coating on a vaso-occlusive device to facilitate sealing
the neck of an aneurysm. For example, U.S. Pat. No. 5,749,894
discloses vaso-occlusive devices having a polymeric coating that
may be melted to seal the neck of an aneurysm within which the
device is deployed. The disclosed method for melting the coating,
however, requires introducing an energy source, e.g., a
light-emitting device, or a radio frequency ("RF") electrical
energy source, into the blood vessel adjacent the aneurysm to
deliver energy to heat and melt the coating.
[0005] The above-referenced U.S. Pat. Nos. 6,187,024 and 5,749,894
are each incorporated by reference herein in their entirety for all
they teach and disclose.
SUMMARY
[0006] In accordance with one aspect of the invention, a
vaso-occlusive device includes a material which, after the device
is implanted in a body cavity, is activated by a source of energy
external to the body to cause heating of the device. By way of
non-limiting example, in one embodiment, the occlusive device is
provided with a highly resistive ferrous material, which is heated
by a pulsed magnetic field applied by an external magnetic
resonance imaging ("MRI") machine. For example, the ferrous
material may be embedded or otherwise carried in or by a
vaso-occlusive coil, or a coating thereon.
[0007] Heating of the occlusive device may be performed as an end
in itself, i.e., to enhance the formation of a blood thrombus
embolism in the cavity, or to improve the long term healing
response of the thrombus and/or surrounding aneurysmal tissue,
after the device is implanted. Additionally or alternatively, the
increase in device temperature may cause a coating on the device to
at least partially melt or soften, thereby releasing or otherwise
activating a therapeutic or diagnostic agent within the cavity.
Further additionally or alternatively, the heating of the device
may cause the device, or portions thereof, to at least partially
melt and fuse together to stabilize the vaso-occlusive device in a
three-dimensional (delivery) shape in the cavity.
[0008] Other aspects and features of the invention will become
apparent from consideration of the following description taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The drawings illustrate the design and utility of preferred
embodiments of the invention, in which similar elements are
referred to by common reference numerals, and in which:
[0010] FIG. 1A is a schematic view of a system for embolizing a
cavity within a patient's body, in accordance with one embodiment
of the invention.
[0011] FIG. 1B is a cross-sectional detail of the patient's body,
showing a vaso-occlusive device being delivered into an
aneurysm.
[0012] FIGS. 2A and 2B are side views of an exemplary embodiment of
a vaso-occlusive device constructed in accordance with the
invention.
[0013] FIGS. 3A-3C are cross-sectional views of a patient's body,
illustrating a method for treating an aneurysm performed in
accordance with embodiments of the invention.
[0014] FIGS. 4A and 4B are partial cross-sectional views of further
exemplary embodiments of vaso-occlusive devices constructed in
accordance with a further aspect of the invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0015] Turning to the drawings, FIGS. 1A and 1B depict a system 10
for embolizing and/or occluding a cavity within a body 90, e.g., an
aneurysm 92 extending from a blood vessel 94. Generally, the system
10 includes a vaso-occlusive device 20, a delivery catheter 30, and
a magnetic resonance imaging ("MRI") machine 40.
[0016] In an exemplary embodiment, such as that shown in FIGS. 2A
and 2B, the vaso-occlusive device 20 includes an elongate helical
coil 22 that assumes a delivery configuration (shown in FIG. 2A)
when constrained in the delivery catheter 30, and a
three-dimensional deployed configuration (shown in FIG. 2B) when
placed in a body cavity, e.g., in aneurysm 92. The coil 22 may be
formed by first winding a small, flexible wire into a linear
helical form defining the delivery configuration, using known heat
treatment methods. Once the delivery shape is set, the coil 22 is
wound into a deployed configuration, e.g., by winding the coil 22
onto a mandrel (not shown) and heat treating the coil 22, using
known methods. Thus, when the coil 22 is free from external forces,
it assumes a relaxed, three-dimensional deployed configuration, as
shown in FIG. 2B. It will be appreciated by those skilled in the
art that the coil 22 may be biased to assume a variety of
predetermined or random shapes in the deployed configuration.
Alternatively, a substantially straight wire or filament, or braid
of wires or filaments may be provided instead of the helical coil
configuration. Additional information on methods for manufacturing
vaso-occlusive devices suitable for constructing embodiments of the
present invention may be found in U.S. Pat. No. 6,322,576 to
Wallace et al., the disclosure of which is incorporated herein by
reference for all that it teaches and discloses.
[0017] The coil 22 may be formed from a variety of materials, e.g.,
metals, polymers, alloys, or composites thereof. In one embodiment
of the invention, described in greater detail blow, the coil 22
includes ferrous material, causing the coil 22 to be heated by
activation of the MRI machine to apply a pulsed magnetic field on
the device after it is implanted at a selected occlusion site in
the vasculature.
[0018] In addition, the coil 22 preferably includes radiopaque
material, such as metals and/or polymers. Suitable metals and
alloys for the wire defining the coil 22 may include the platinum
group metals, especially platinum, rhodium, palladium, and rhenium,
as well as tungsten, gold, silver, tantalum, and alloys of these
metals. These metals have significant radiopacity and their alloys
may be tailored to accomplish an appropriate blend of flexibility
and stiffness for the coil 22. They are also generally biologically
inert. A platinum/tungsten alloy may be most preferred, with
ferrous material mixed with or carried by the alloy. Additional
suitable materials are described in the above-incorporated U.S.
Pat. No. 6,322,576.
[0019] Additionally or alternatively, the coil 22 may include
radiolucent fibers or polymers (or metallic threads coated with
radiolucent or radiopaque fibers), such as Dacron (polyester),
polyglycolic acid, polylactic acid, fluoropolymers
(polytetrafluoroethylene), Nylon.TM. (polyamide), and/or silk. When
a polymer is used as the major component of the vaso-occlusive
device 20, it may be filled with some amount of radiopaque
material, such as powdered tantalum, tungsten, bismuth oxide,
barium sulfate, and the like. In addition, the ferrous material,
e.g., iron particles, filaments and the like, may be mixed with
and/or embedded in the polymer.
[0020] When the coil 22 is made from a platinum alloy or
superelastic alloy, such as nitinol, or other materials, the
diameter of the wire defining the coil 22 may be between about
0.0005 and 0.006 inch (0.012-0.15 mm). The wire may be wound into a
primary coil having a primary diameter between about 0.005 and
0.025 inch (0.125-0.625 mm), and preferably between about 0.010 and
0.018 inch (0.25-0.45 mm). Such wire may be of an appropriate
diameter to provide sufficient hoop strength to hold the
vaso-occlusive device 20 in place within a chosen body cavity
without distending the wall of the cavity and/or without moving
substantially from the cavity as a result of the repetitive fluid
pulsing experienced within the vascular system.
[0021] The axial length of the delivery configuration of the coil
22 may be between about one half and one hundred centimeters
(0.5-100 cm), and preferably between about two and forty
centimeters (2-40 cm). In the delivery configuration, the coil 22
may have between about ten and seventy five (10-75) turns per
centimeter, and preferably between about ten and forty (10-40)
turns per centimeter.
[0022] In one embodiment, a coating is provided on the coil 22, the
coating having a melting temperature "T.sub.m" or a glass
transition temperature "Tg" that is less than the temperature to
which the vaso-occlusive device 20 is heated by the MRI machine 40.
For example, the coating may have a "T.sub.m" and/or "Tg" of about
80-150.degree. F. Suitable polymeric materials may include
polyalkenes, polymethacrylates, polyacrylates, polyesters,
polyamides, and polysaccharides. Co-polymers, blends, alloys, and
block copolymers of such materials may also be used. Additional
information on suitable coatings are described in the
above-incorporated U.S. Pat. Nos. 5,749,894 and 6,187,024.
[0023] The coating comprises, or otherwise covers, one or more
agents, e.g., a bioactive agent, a collagenous material, and/or
other diagnostic or therapeutic agent(s). Exemplary bioactive
agents may include genes, growth factors, biomolecules, peptides,
oligonucleotides, members of the integrin family, RGD-containing
sequences, oligopeptides, fibronectin, laminin, bitronectin,
hyaluronic acid, silk-elastin, elastin, fibrinogen, and other
basement membrane proteins with bioactive agents. By way of
non-limiting example, the agent(s) may be applied in a first
coating on the coil 22, with a second coating, such as the
polymeric materials described above, applied to substantially cover
or otherwise embed the agent(s) from exposure to the blood pool and
body tissue at the deployment site in the vasculature.
Alternatively, the vaso-occlusive device 20 (e.g., coli 22) may
itself be formed from a polymeric material having with one or more
embedded diagnostic and/or therapeutic agents that are released by
heating of the device, as described in greater detail below.
[0024] In particular, one or more agent(s) may be carried on, or
otherwise embedded in, the vaso-occlusive device 20 without being
initially exposed or otherwise released or activated in the body
upon implantation of the device. This can be advantageous, e.g.,
for preventing the agent(s) from release or activation if the
vaso-occlusive device 20 is exposed within a blood vessel or other
body region where embolization or other treatment effects are
undesired. Only when the coating and/or the coil itself is heated
above its melting and/or glass transition temperature, e.g., when
it is determined that the implant device is placed where desired in
the body cavity, are the agent(s) released or otherwise activated.
For example, the agents may be prevented from making contact with
the blood/tissue in the body cavity until released by the heating
of the implant device (as described above). Additionally or
alternatively, the agents may be exposed to the blood/tissue in the
cavity, but dormant until heated (i.e., by conductive heating from
the heated ferrous material) above a critical temperature
threshold, activating (with the heat as the catalyst) the bioactive
agent.
[0025] Returning to FIG. 1A, the MRI machine 40 includes a static
field magnet 42, a gradient field amplifier 44 and a radio
frequency ("RF") transmitter/receiver 46. The magnet 42 includes an
internal lumen region for receiving the patient 90, and may provide
a static, relatively homogeneous magnetic field over the patient
90. Alternatively, an open-MRI machine or other MR device may be
used, as is well-known. During conventional operation, the gradient
field amplifier 44 generates pulsed magnetic field gradients that
vary the static magnetic field, and the RF transmitter 46 transmits
RF pulse sequences over the patient's body to cause the patient's
tissues to emit MR response signals. The MR response signals may be
used to generate images of the patient's body 90, as is
well-known.
[0026] When the MRI machine 40 is activated, the pulsed magnetic
field generated by the magnet 42 and gradient field amplifier 44
will agitate the ferrous material in the vaso-occlusive device 20,
thereby causing the ferrous material to heat. Other portions of the
vaso-occlusive device 20, e.g., a coating and/or polymeric material
defining the coil 22 itself, are heated by conduction from the
heated ferrous material above their "T.sub.m" and/or "T.sub.g,"
causing the coating and/or polymeric material portions to at least
partially melt or soften. Additionally or alternatively, heat
generated by the interaction between the MRI device 40 and the
ferrous material in the vaso-occlusive device 20 heats the
surrounding blood or tissue to enhance embolization of the site
and/or promote improved long term healing of the embolism and/or
surrounding aneurysmal tissue. Notably, a coating on the occlusive
device may itself include ferrous material.
[0027] More particularly, the pulsed magnetic field can heat the
ferrous material through at least two mechanisms. First, the
material can be heated due to hysteresis losses associated with the
material being alternatively energized with positive and negative
energy fields; i.e., as some materials are less efficient in
responding to the alternating polarization, resulting in current
losses which produce heat. Materials that are poor conductors, such
as ferrous materials, produce more heat effects than highly
conductive materials such as copper, platinum or aluminum. Other
factors that effect hysteresis losses include the flux density and
the MR frequency of the selected materials.
[0028] A second mechanism for the generation of heat involves
conduction losses. The MR machine produces a conduction field
around the device, thereby producing a voltage potential across the
device. This voltage potential produces eddy currents in the
occlusive device. Some materials and some implant device
constructions are more conductive than others. Less conductive
implants will result in more heat being generated. By way of
example, flat ribbon material, rather than round wire stock, will
increase resistance (and, thus, heating), as will using ferrous
materials over conductive materials such as copper, platinum or
aluminum.
[0029] Turning to FIGS. 3A-3C, a method for embolizing and/or
occluding an aneurysm 92 is illustrated that employs the system 10
shown in FIG. 1A. In this exemplary method, the vaso-occlusive
device 20 may include a bioactive agent, collagenous material,
and/or other therapeutic and/or diagnostic agent embedded within or
beneath a coating on the coil 22.
[0030] Initially, the delivery catheter 30 is introduced into the
patient's body 90 from a percutaneous entry site into a peripheral
artery, such as the femoral or carotid arteries (not shown), as is
well-known. The delivery catheter 30 may be advanced over a
guidewire or other rail (not shown) previously placed within the
patient's vasculature using known methods. The delivery catheter 30
is advanced through the patient's vasculature, until a distal end
32 of the catheter 30 is disposed within a blood vessel 94 adjacent
the aneurysm 92.
[0031] Once the catheter 30 is properly positioned, the
vaso-occlusive device 20 is advanced through a lumen 34 of the
catheter 30 into the aneurysm 92, as shown in FIG. 3A. As the
vaso-occlusive device 20 is deployed in the aneurysm, it assume a
three-dimensional, deployed configuration. Preferably, the deployed
configuration is selected such that the vaso-occlusive device 20
substantially fills the aneurysm 92. Once the vaso-occlusive device
20 is fully deployed within the aneurysm 92, as shown in FIG. 3B,
the delivery catheter 30 is removed. Depending on the circumstances
(e.g., size and condition of the aneurysm), a treating physician
will deploy multiple occlusive devices into a single aneurysm, as
is well-known. Additional information on apparatus and methods that
may be suitable for delivering the vaso-occlusive coil 20 is found
in U.S. Pat. No. 4,994,069 to Ritchart et al., which is
incorporated by reference herein for all it teaches and discloses,
as well as the other above-incorporated U.S. patents.
[0032] Turning to FIG. 3C, once the occlusive coil 22 is implanted
and the delivery catheter 30 removed from the body, the MRI machine
40 is activated to at least partially melt or sufficiently soften
the coating on the coil 22. This may involve transferring the
patient 90 from a catheter lab or other location where the
vaso-occlusive device 20 was implanted into a MRI room.
[0033] As explained above, once the patient 90 is disposed within
the MRI magnet 42, the gradient field amplifier 44 (not shown in
FIG. 3C, see FIG. 1A) is activated to generate magnetic energy
(represented by arrows 48 in FIG. 3C), which interacts with ferrous
material in the coil 22 and/or coating to heat the vaso-occlusive
device 20. Generally, the MRI machine 40 is activated for a
predetermined time, e.g., between about 3 seconds to 20 minutes, to
heat the vaso-occlusive device 20 and/or coating to a desired
temperature. For example, the vaso-occlusive device and/or coating
may be heated to a temperature of at least about 0.150.degree. F.
(about 40.degree. C.)
[0034] As the coating reaches its "T.sub.m" and/or "T.sub.g" the
coating may melt and/or flow, thereby releasing or otherwise
activating one or more diagnostic or therapeutic agent(s) 28
carried in or beneath the coating. For example, the coating may
include a thrombogenic agent that enhances embolization of blood
when released within the aneurysm 92. In addition or alternatively,
the coating may include one or more agents that remain
substantially inert until heated above a predetermined activation
temperature. Further additionally or alternatively, the MRI machine
40 may be activated for the to heat the vaso-occlusive device 20 in
order to heat blood or other material within the aneurysm 92 and/or
tissue surrounding the aneurysm 92, even in the absence of such
agent(s). Such heating may accelerate coagulation of blood or other
fluid within the aneurysm 92 and/or may cause the surrounding
tissue to contract, e.g., to reduce the size of the aneurysm 92,
and promote an improved long term healing response.
[0035] In accordance with a further aspect of the invention, in an
alternate embodiment, at least a portion of the vaso-occlusive
device 20 is formed from a material that melts or is otherwise
sufficiently softened when heated. In this embodiment, the MRI
machine 40 is activated for sufficient time to cause at least a
portion of a coating and/or coil of the vaso-occlusive device 20 to
melt and/or flow together. When the MRI machine 40 is deactivated,
the coil cools, and substantially solidifies, thereby fusing
together melted/softened portions of the vaso-occlusive device 20
in its deployed configuration in the aneurysm 92. This fusion
stabilizes the vaso-occlusive device 20 in its deployed
configuration, helping prevent the device from moving back towards
a delivery and/or other generally linear shape.
[0036] FIGS. 4A and 4B are partial cross-sections (or cutaways) of
further embodiments of MR-activated, embolic implant devices 100
and 100', respectively, constructed in accordance with a further
aspect of the present invention. The devices 100 and 100' are each
made up of a helically wound occlusive coil 102 having a first end
104 and a second end 106. While the coil 102 is depicted in FIGS.
4A and 4B as made from a round wire, i.e., having a substantially
circular cross-section, the coil 102 may alternatively be made from
a differently shaped wire, e.g., a flat wire having a rectangular
cross-section. The coil 102 is preferably made of platinum, and may
be provided with a heat-releasable and/or activated agent coating
(not shown), as discussed above. Additionally or alternately, a
heat-releasable and/or activated agent coating may be provided on
the filament 108, 114.
[0037] The coil 102 forms a central lumen, through which a ferrous
material filament 108 (FIG. 4A), 114(FIG. 4B) is located, the
filament being fixed to the respective first and second ends 104
and 106 of the coil 102. In this manner, the filament 108, 114 acts
as a heating element upon application of an AC magnetic field by an
MRI machine, as discussed above. In particular, the highly
conductive (preferably platinum) coil 102 generates a corresponding
highly efficient induction field, which heats the highly resistive
ferrous material filament 108, 114 in the coil lumen. Thermal
energy in the heated filament is then transferred by convection to
the coil 102 and surrounding blood pool and tissue, which has the
benefits/effects previously described.
[0038] Further additionally or alternately, at least a portion of
the coil 102 may be formed from a material that melts or
substantially softens when heated, as described above. In this
case, fusing points of the coil 102 in its deployed configuration
may be determined by locations that the ferrous filament is
attached, since these attachment points on the coil 102 will heat
the most. It will be appreciated from the present disclosure that
the features of a heat-releasable and/or activated agent and
structural fusing of the occlusive coil may be provided separately
or together in a single, implantable device.
[0039] The filament 108, 114 may also (optionally) serve as a
stretch resisting member, as taught, for example, in U.S. Pat. No.
5,853,418, which is fully incorporated by reference herein for all
that it teaches and discloses. In certain circumstances, it may be
desirable to attach the filament 108, 114 only to one of the two
ends 104, 106, or alternately (or additionally) to at least one
site between the to ends, or to neither of the two ends. Of course,
for attaining stretch resistance, if so desired, the filament 108,
114 must be attached to at least two points on the coil 102.
[0040] The ferrous filament 108, 114 may be constructed in various
ways. For example, the filament 108, 114 may comprise thermoplastic
or thermosetting having a bundle of threads or a single filament
with one or more metallic ferrous strands formed therein. The
filament 108 of the variation shown in FIG. 4A is formed as a
ribbon; the filament 114 shown in FIG. 4B is formed as a helically
wound coil; in both cases that is soldered, brazed, glued, or
otherwise fixedly attached to the first and second coil ends 104
and 106.
[0041] In further alternative embodiments, other devices or
processes may be employed for in-situ heating of vaso-occlusive
devices in accordance with the present invention. For example, an
ultrasound device (not shown) may be provided, e.g., including a
piezoelectric transducer that may be placed in contact with the
patient's skin overlying an aneurysm, lumen, or other cavity where
a vaso-occlusive device has been implanted. If desired, an acoustic
gel or other material may be provided between the transducer and
the patient's skin to enhance acoustically coupling the transducer
to the patient, as is known in the art.
[0042] Acoustic energy may be delivered from the ultrasound device
through the patient's skin and intervening tissue to the cavity to
heat the vaso-occlusive device. The energymay be focused or
generally directed into the patient's body using known methods. The
acoustic energy may be transferred to heat energy when it is
absorbed by the vaso-occlusive device and/or surrounding tissue to
heat the vaso-occlusive device. The vaso-occlusive device may
include materials that enhance acoustic energy absorption and/or
attenuation in a predetermined manner to ensure adequate heating of
the vaso-occlusive device.
[0043] In further alternate embodiments, a source of electrical
energy, e.g., a radio frequency ("RF") generator, may be provided
adjacent the patient's skin. Electrical energy may be delivered
into the patient's body to inductively heat the vaso-occlusive
device, as is known to those skilled in the art.
[0044] Although the present invention has been described with
reference to occlusion and treatment of vasculature sites, such as
aneurysms, those skilled in the art will recognize that the
methodology of heating an implanted device using an energy source
outside of the body could be used for other types of conditions,
such as for heating tumors, releasing bioactive agents (e.g., using
a low level of heating energy) at any number of intra-body
locations, as well as to heat other types of implants, e.g., stents
and the like, to enhance patient treatment.
[0045] While the invention is susceptible to various modifications,
and alternative forms, specific examples thereof have been shown in
the drawings and are herein described in detail. It should be
understood, however, that the invention is not to be limited to the
particular forms or methods disclosed, but to the contrary, the
invention is to cover all modifications, equivalents and
alternatives falling within the scope of the appended claims.
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